Altimeter or barometer



June 15, R K. STOUT ETAL ALTIMETER OR BAROMETER Filed June l5, 1940Olfillillllillrllilrf P4 as Y Patented June 15, 1943 QFFICE ALTMETER ORBARON/ESTER Raymond l. Stout and Charles L. Panta,

Dayton, Ohio Atenea-.aon .time 15, 1346 'serai sienes (ci. isa-i)(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) 4 Claims.

' 'ihe invention described herein may be manuiactured and used by or forthev Government for governmental purposes, without the payment to us ofany royalty thereon.

The present invention relates to a'ltimeters' or barometers or otherinstruments fordetermining atmospheric pressure.

Our invention embodies an arrangement of parts, making up an altimeterof a type which may be carried in the pocket. the device will bemaintained at approximately body heat eliminates the necessity foraccurate temperature correction, and makes for a simplicity not hithertoobtained in the art.

When used as an altimeter the device included in our invention has'meansfor adjusting for altitude above sea level of the starting point and forchange in barometric pressure.

` The use of the device as an altimeter is particularly adaptable to useby passengers on airliners, mountain travel either on foot or byautomobile, etc.

When used as a barometer our device includes lmeans for adjusting theZero point to accommodate height above sea level.

The use of the device. as a barometer is val'- uable for fishermen,boatrnen and the like for predicting weather.

One embodiment of our invention is shown and described herein but we donot mean to restrict the invention to any particular size or shape ofparts consistent with a device suitable for carrying in the pocket, nordo we intend to restrict the invention to 'the use of any particularmaterial or materials for the fabrication thereof.

The invention will be more clearly understood by reference to thedrawing, in which:

Figure 1 is a front View, partially in crosssection, showing thevcomplete altimeter or barometer.

Figure 2 is a fragmentary sectional elevation of the device showing thediaphragm in the sea level position.

Figure 3 is a fragmentary sectional elevation of the device, showing thediaphragm in the high altitude position.

In general our invention uses a mercury coln umn, supported by a partialvacuum and sealed by a rubber or synthetic rrubber diaphragm to indicatealtitude. The invention also embodies means for adjusting the zeropoint. The use of Aa mercury column and a settable zero or level pointis old in the art but the conventional barometer would be impracticalfor .indicating The fact that f theY altitude of aircraft as it normallyrequires a 29 inch mercury column and an exposed sump or mercury pot atthe bottom of the column. In the conventional device the mercury will beat the top of the tubular container at seat level and the mercury willdrop, for example, ap" proximately 16 inches for ,a change of 15,000feet in altitude, developing a perfect vacuum on top ofV the column asthe mercury moves. In case the graduations would be a straight linefunction of the change in altitude or atmospheric pressure. Using thesame gure (155Mo feet) altitude as an example, our inven tion willprovide an altimeter in which the Inercury column will move only 21/2inches, at this altitude, from the sea level point. This action isobtained by providing only a parta-l vacuum over the column of mercury.We also substitute a synthetic rubber, flexible diaphragm for theymercury sump, which in combination with the reduction of scalementioned above makes a compact unit.

In barometers using a solid mercury columnl a change in temperaturecauses an expansion or contraction of the mercury and thus causes a riseor fall in the height of the column. This. of course, necessitates atemperature correction in o-r-der to determine the true reading of theinstrument. 'in our device, however, the small `quantity of air whichvpresentin the partial vacuum existing above the mercury, `expands landcontracts in response to changes in temperature so as to counteract theexpansion or contraction of the mercury. For example, if the temperature increases, the mercury expands and tends .to risev in the tube, butthe air present in the space .above the mercury also expands and tendsto force the mercury down in the tube. While the coeicient of expansionof air is greater than that of mercury, yet the air, in this case. is sorareiied that its expansion is small and only sufcient to overcome theexpansion of the mercury, with the result that changes in temperature donot alter the .readings ,of the instrument.k This, together with thefact that the device is intended to be carried in the pocket. where thetemperature remains practically uniform, makes it unnecessary to applyany tem- `perature correction to the readings.

use of the device is simple the operator can read directly, the altitudeabove sea level or the altitude above any present point. The latter isobtained by shifting the Zero or reference point.

In order to use our device as a barometer it is only necessary tocalibrate the scale in inches of mercury, or in Storm, Fain and Cleaninstead of in feet of altitude. If desired, the scale may be adjustedalong the tube to correct for the height above sea level.

Fig. 1 shows an embodiment of our device drawn to full scale. 'Iheconvenient size and compactness of the pocket altimeter is at onceapparent from the drawing. It is of approximately the same size andshape as a fountain pen and may be furnished with a clip so as to becarried in the pocket in the same manner as a pen or pencil. The extremesimplicity of the instrument, both in design and in features ofconstruction, make for an inexpensive and reliable altimeter orbarometer. As shown in Fig. l, the instrumentl is comprised of a tubularelement for a mercury column having an enlarged upper1 end I5, anenlarged lower end 4, and a narrow tubular portion 5 connecting theupper and lower portions 4 and 6. The tubular element may be made ofglass or any other suitable transparent material, such as a plastic, andis provided with a small bore 4 extending from a recess S in the end 6to a cavity 'I formed in the bottom of the lower portion 4. The top ofthe recess E is closed by a plug 8 having a hole S. A diaphragm lil madeof rubber, rubber substitute, or other suitable resilient material isplaced over the cavity 'I and sealed to the portion 4 of the element bymeans of rubber bands and cement II. This forms a mercury sump which mayrespond t changes in atmospheric pressure by means of the resilientdiaphragm I. The sump and part of the bore 4 are lled with mercury and aportion of the air in the space above the mercury is then exhaustedthrough the small hole 9 in the plug The hole 9 is closed by a plug 9after a proper degree of vacuum has been attained over the mercury.

In order to protect the tubular element for the mercury column againstinjury and also to provide a scale for reading the height of the mercuryin the reduced portion of the element, a housing I, formed either ofmetal or plastic, is provided. A slot 2 is out out of the housing so asto expose the tubular portion 5. Scale indicia 2 are marked off alongthe edge of the slot, these indicia being either in feet of altitude,inches of mercury, or in any other suitable units. rIhe inside diameterof housing I is equal to the diameter of the enlarged portion 4, and thehousing is provided with a slit 3 so as to enable it to be frictionallyheld in place on the element. Thus, the housing and its scale may beadjusted along the tube 5 when such adjustment is necessary ordesirable. A cap I2 covers the lower end of the instrument in order toprotect the diaphragm I Il from injury or from contact with nearbyobjects which might alter the reading of the device. This cap may bemade of any suitable material such as a plastic or metal and is suppliedwith an air vent I3 to insure that the interior of the cap will alwaysbe at the same pressure as the outside atmosphere. Cap I 2 is rmlyfastened to the lower end 4 of the element in order that the housing Imay be shifted along the column without removing the cap. It may befastened to the element in any desired manner, a convenient way beingsimply te cement it to the element in the vicinity of II.

Figure 2 shows the diaphragm I0 in a sea level position or against thecolumn 4 due to high atmospheric pressure.

It will be noted that in Fig. 3 the diaphragm is bulged away from thecolumn, which would be the result of reduced atmospheric pressure.

Having disclosed and described our invention, we claim:

1. A pocket barometer of the type utilizing a partial vacuum above theindicating fluid, comprising a short tubular element having enlarged endportions connected by an intermediate portion of reduced diameter, theupper end portion being slightly smaller in diameter than the lower endportion, a reentrant surface formed in the end of said lower endportion, a resilient diaphragm located over` the mouth of said reentrantsurface, a protective sleeve having an inside diameter substantiallyequal to that of said lower end portion whereby the sleeve may beslipped over the upper and intermediate portions of said tubular elementand frictionally held in place on the lower end portion thereof, saidsleeve being provided with a longitudinally extending slot and scalemarkings located along said slot whereby said markings may be adjustedrelative to said tubular element by moving said sleeve on the lower endportion of said element, and a tubular cap tting over said lower endportion and over the lower portion of said sleeve for the purpose ofprotecting said diaphragm from injury or disturbance.

2. A pocket-sized atmospheric pressure measuring device of the typeutilizing a partial vacuum above the indicating fluid, comprising atubular element having a reentrant surface formed in one end thereof, aresilient diaphragm located over the mouth of said reentrant surface, aprotective sleeve surrounding said element and having a longitudinallyextending slot with scale markings provided along said slot, said sleevebeing adjustably retained on said tubular element so as to enable saidmarkings to be adjusted relative to said tubular element, and an end capcovering the end of said tubular element which contains said reentrantsurface for the purpose of protecting said diaphragm from injury ordisturbance.

3. A pocket-sized atmospheric pressure measring device of theV typeutilizing a partial vacuum above the indicating fluid, comprising atubular element having enlarged end portions connected by anVintermediate portion of reduced diameter, a reentrant surface formed inthe end of one of said end portions, a resilient diaphragm located overthe mouth of said reentrantl surface, a protective sleeve surroundingsaid element and having a longitudinally extending slotwith scalemarkings provided along said slot, said sleeve being adjustably retainedupon said tubular element so as to enable said markings to be adjustedrelative to said tubular element, and an end cap covering the end ofsaid tubular element which contains said reentrant surface for thepurpose of protecting said diaphragm from injury or disturbance.

4. A pocket-sized atmospheric pressure measuring device of the typeutilizing a partial vacuum above the indicating fluid, comprising atubular element having enlarged end portions connected by anintermediate portion of reduced diameter, one of said end portions beingslightly larger in diameter than the other of said end portions, areentrant surface formed in the end of one of said end portions, aresilient diaphragm located over the mouth of said reentrant sur;

face, a protective sleeve surrounding said element tion containing saidreentrant surface and also and having a longitudinally extending slotwith over the neighboring end of said sleeve for the scale markingsprovided along said slot, said purpose of protecting said diaphragm frominsleeve being adjustably retained on the larger jury or disturbance.

of said end portions so as to enable said scale 5 to be adjustedrelative to said tubular element, RAYMOND K. STOUT. and an end capadapted to t over the end por- CHARLES L. PAULUS.

